Optimization and Evaluation of Enzyme-Assisted Alkaline Extraction of Hemp Protein

With the rise in popularity of plant proteins, the appeal of hemp protein is increasing across commercial and scientific domains. Despite potentially appealing sustainability and nutritional attributes, the poor solubility of hemp protein presents extraction and processing challenges. High alkalinity is required to ensure a high protein extraction yield. Such high alkalinity is detrimental to the protein quality and functionality. Therefore, mild extraction conditions involving enzyme assistance were explored. This study aimed to optimize and evaluate an enzyme-assisted extraction of hemp protein from defatted hemp flour under mild pH conditions.

Hemp seeds (X-59) were dehulled, defatted, and milled prior to protein extraction. Protein extraction from the defatted flour was performed with and without glutaminase, a non-hydrolytic enzyme, following alkaline solubilization at pH 7, 8, 9, 10, and 11 and precipitation at pH 5. Protein yield, purity, and solubility of all resulting hemp protein isolate (HPI) samples were evaluated. Protein structure and functionality were characterized for HPI produced following both enzyme-assisted (E-HPI) and reference alkaline extraction (R-HPI).

The success of the enzyme treatment was assessed based on the protein’s yield, purity, and protein functionality. At solubilization pH 8, enzyme-assisted alkaline extraction had over 8 times higher protein yield and significantly higher protein purity compared to the reference alkaline extraction. The solubility of E-HPI at pH 7 under both heated and non-heated conditions was significantly higher  compared to R-HPI produced from pH 8 to 11. E-HPI had superior techno-functional properties.

This work demonstrated the success of hemp protein extraction at mild pH with a preceding deamidation step. Enzyme-assisted extraction at mild alkalinity resulted in a high protein extraction yield, and e successfully improved HPI functionality, especially solubility. These findings will provide guidance for the industrial production of a functional HPI for use in various food applications.